Systems and methods for simulating a reaction force from a virtual object are known to provide haptic feedback to a user in response to an input force applied to the virtual object by the user. An example of a system for providing such haptic feedback is described in WO 2005/043365 A. However, if the device on which the virtual object is displayed has its own weight which is felt by the user and/or is a portable or mobile device, there is no currently satisfactory way to simulate a reaction force from a virtual object displayed on such a device. For example, WO 2009/138814 only describes providing haptic feedback to a user in order to identify functions or the results of motion of the device itself, and in particular of a mobile device, rather than from a virtual object which is displayed on the device.